diff --git a/user_guide_src/source/cli/cli.rst b/user_guide_src/source/cli/cli.rst
index 0e5cf61640..f99ff92d7a 100644
--- a/user_guide_src/source/cli/cli.rst
+++ b/user_guide_src/source/cli/cli.rst
@@ -49,7 +49,7 @@ in it::
 		}
 	}
 
-Then save the file to your **application/Controllers/** directory.
+Then save the file to your **app/Controllers/** directory.
 
 Now normally you would visit the your site using a URL similar to this::
 
diff --git a/user_guide_src/source/cli/cli_commands.rst b/user_guide_src/source/cli/cli_commands.rst
index d55f2cb43d..f74c8ebcc8 100644
--- a/user_guide_src/source/cli/cli_commands.rst
+++ b/user_guide_src/source/cli/cli_commands.rst
@@ -16,7 +16,7 @@ building out custom code generators for your company.
 Running Commands
 ****************
 
-Commands are run from the command line, in the root directory. The same one that holds the **/application**
+Commands are run from the command line, in the root directory. The same one that holds the **/app**
 and **/system** directories. A custom script, **spark** has been provided that is used to run any of the
 cli commands::
 
@@ -67,7 +67,7 @@ File Location
 =============
 
 Commands must be stored within a directory named **Commands**. However, that directory can be located anywhere
-that the :doc:`Autoloader </concepts/autoloader>` can locate it. This could be in **/application/Commands**, or
+that the :doc:`Autoloader </concepts/autoloader>` can locate it. This could be in **/app/Commands**, or
 a directory that you keep commands in to use in all of your project development, like **Acme/Commands**.
 
 .. note:: When the commands are executed, the full CodeIgniter cli environment has been loaded, making it
@@ -77,7 +77,7 @@ An Example Command
 ==================
 
 Let's step through an example command whose only function is to report basic information about the application
-itself, for demonstration purposes. Start by creating a new file at **/application/Commands/AppInfo.php**. It
+itself, for demonstration purposes. Start by creating a new file at **/app/Commands/AppInfo.php**. It
 should contain the following code::
 
     <?php namespace App\Commands;
diff --git a/user_guide_src/source/concepts/mvc.rst b/user_guide_src/source/concepts/mvc.rst
index 9cc6b16dcd..fecfba631d 100644
--- a/user_guide_src/source/concepts/mvc.rst
+++ b/user_guide_src/source/concepts/mvc.rst
@@ -18,7 +18,7 @@ the data storage.
 
 At their most basic, controllers and models are simply classes that have a specific job. They are not the only class
 types that you can use, obviously, but the make up the core of how this framework is designed to be used. They even
-have designated directories in the **/application** directory for their storage, though you're free to store them
+have designated directories in the **/app** directory for their storage, though you're free to store them
 wherever you desire, as long as they are properly namespaced. We will discuss that in more detail below.
 
 Let's take a closer look at each of these three main components.
@@ -37,11 +37,11 @@ Views get the data to display from the controllers, who pass it to the views as
 with simple ``echo`` calls. You can also display other views within a view, making it pretty simple to display a
 common header or footer on every page.
 
-Views are generally stored in **/application/Views**, but can quickly become unwieldy if not organized in some fashion.
+Views are generally stored in **/app/Views**, but can quickly become unwieldy if not organized in some fashion.
 CodeIgniter does not enforce any type of organization, but a good rule of thumb would be to create a new directory in
 the **Views** directory for each controller. Then, name views by the method name. This makes them very easy find later
 on. For example, a user's profile might be displayed in a controller named ``User``, and a method named ``profile``.
-You might store the view file for this method in **/application/Views/User/Profile.php**.
+You might store the view file for this method in **/app/Views/User/Profile.php**.
 
 That type of organization works great as a base habit to get into. At times you might need to organize it differently.
 That's not a problem. As long as CodeIgniter can find the file, it can display it.
@@ -61,7 +61,7 @@ it's saved to meet company standards, or formatting a column in a certain way be
 By keeping these business requirements in the model, you won't repeat code throughout several controllers and accidentally
 miss updating an area.
 
-Models are typically stored in **/application/Models**, though they can use a namespace to be grouped however you need.
+Models are typically stored in **/app/Models**, though they can use a namespace to be grouped however you need.
 
 :doc:`Find out more about models </models/model>`
 
@@ -77,7 +77,7 @@ The other responsibility of the controller is to handle everything that pertains
 authentication, web safety, encoding, etc. In short, the controller is where you make sure that people are allowed to
 be there, and they get the data they need in a format they can use.
 
-Controllers are typically stored in **/application/Controllers**, though they can use a namespace to be grouped however
+Controllers are typically stored in **/app/Controllers**, though they can use a namespace to be grouped however
 you need.
 
 :doc:`Find out more about controllers </incoming/controllers>`
diff --git a/user_guide_src/source/concepts/services.rst b/user_guide_src/source/concepts/services.rst
index 15e6509df1..f0d589078e 100644
--- a/user_guide_src/source/concepts/services.rst
+++ b/user_guide_src/source/concepts/services.rst
@@ -79,7 +79,7 @@ create a new class that implements the ``RouterCollectionInterface``::
 		// Implement required methods here.
 	}
 
-Finally, modify **/application/Config/Services.php** to create a new instance of ``MyRouter``
+Finally, modify **/app/Config/Services.php** to create a new instance of ``MyRouter``
 instead of ``CodeIgniter\Router\RouterCollection``::
 
 	public static function routes()
diff --git a/user_guide_src/source/concepts/structure.rst b/user_guide_src/source/concepts/structure.rst
index a0d370d22e..66818a7298 100644
--- a/user_guide_src/source/concepts/structure.rst
+++ b/user_guide_src/source/concepts/structure.rst
@@ -8,18 +8,18 @@ can change to meet the needs of your application.
 Default Directories
 ===================
 
-A fresh install has six directories: ``/application``, ``/system``, ``/public``,
+A fresh install has six directories: ``/app``, ``/system``, ``/public``,
 ``/writable``, ``/tests`` and ``/docs``.
 Each of these directories has a very specific part to play.
 
-application
------------
-The ``application`` directory is where all of your application code lives. This comes with a default directory
+app
+---
+The ``app`` directory is where all of your application code lives. This comes with a default directory
 structure that works well for many applications. The following folders make up the basic contents:
 
 .. code-block:: none
 
-	/application
+	/app
 		/Config         Stores the configuration files
 		/Controllers    Controllers determine the program flow
 		/Database       Stores the database migrations and seeds files
@@ -31,7 +31,7 @@ structure that works well for many applications. The following folders make up t
 		/ThirdParty     ThirdParty libraries that can be used in application
 		/Views          Views make up the HTML that is displayed to the client.
 
-Because the ``application`` directory is already namespaced, you should feel free to modify the structure
+Because the ``app`` directory is already namespaced, you should feel free to modify the structure
 of this directory to suit your application's needs. For example, you might decide to start using the Repository
 pattern and Entity Models to work with your data. In this case, you could rename the ``Models`` directory to
 ``Repositories``, and add a new ``Entities`` directory.
@@ -40,7 +40,7 @@ pattern and Entity Models to work with your data. In this case, you could rename
 		routing to controllers, and will need to define all of your routes in the routes file.
 
 All files in this directory live under the ``App`` namespace, though you are free to change that in
-**application/Config/Constants.php**.
+**app/Config/Constants.php**.
 
 system
 ------
@@ -84,4 +84,4 @@ Modifying Directory Locations
 -----------------------------
 
 If you've relocated any of the main directories, you can change the configuration
-settings inside ``application/Config/Paths``.
+settings inside ``app/Config/Paths``.
diff --git a/user_guide_src/source/database/configuration.rst b/user_guide_src/source/database/configuration.rst
index 6ef1aa0db6..458d22a1e5 100644
--- a/user_guide_src/source/database/configuration.rst
+++ b/user_guide_src/source/database/configuration.rst
@@ -8,7 +8,7 @@ Database Configuration
 
 CodeIgniter has a config file that lets you store your database
 connection values (username, password, database name, etc.). The config
-file is located at application/Config/Database.php. You can also set
+file is located at app/Config/Database.php. You can also set
 database connection values in the .env file. See below for more details.
 
 The config settings are stored in a class property that is an array with this
diff --git a/user_guide_src/source/dbmgmt/migration.rst b/user_guide_src/source/dbmgmt/migration.rst
index b107934d94..1bb28167ea 100644
--- a/user_guide_src/source/dbmgmt/migration.rst
+++ b/user_guide_src/source/dbmgmt/migration.rst
@@ -11,7 +11,7 @@ need to be run against the production machines next time you deploy.
 The database table **migration** tracks which migrations have already been
 run so all you have to do is update your application files and
 call ``$migration->current()`` to work out which migrations should be run.
-The current version is found in **application/Config/Migrations.php**.
+The current version is found in **app/Config/Migrations.php**.
 
 .. contents::
   :local:
@@ -36,7 +36,7 @@ method taken. Two numbering styles are available:
   the preferred scheme in CodeIgniter 3.0 and later.
 
 The desired style may be selected using the ``$type`` setting in your
-*application/Config/Migrations.php* file. The default setting is timestamp.
+*app/Config/Migrations.php* file. The default setting is timestamp.
 
 Regardless of which numbering style you choose to use, prefix your migration
 files with the migration number followed by an underscore and a descriptive
@@ -50,7 +50,7 @@ Create a Migration
 ******************
 
 This will be the first migration for a new site which has a blog. All
-migrations go in the **application/Database/Migrations/** directory and have names such
+migrations go in the **app/Database/Migrations/** directory and have names such
 as *20121031100537_Add_blog.php*.
 ::
 
@@ -86,7 +86,7 @@ as *20121031100537_Add_blog.php*.
 		}
 	}
 
-Then in **application/Config/Migrations.php** set ``$currentVersion = 20121031100537;``.
+Then in **app/Config/Migrations.php** set ``$currentVersion = 20121031100537;``.
 
 The database connection and the database Forge class are both available to you through
 ``$this->db`` and ``$this->forge``, respectively.
@@ -108,7 +108,7 @@ Database Groups
 ===============
 
 A migration will only be run against a single database group. If you have multiple groups defined in
-**application/Config/Database.php**, then it will run against the ``$defaultGroup`` as specified
+**app/Config/Database.php**, then it will run against the ``$defaultGroup`` as specified
 in that same configuration file. There may be times when you need different schemas for different
 database groups. Perhaps you have one database that is used for all general site information, while
 another database is used for mission critical data. You can ensure that migrations are run only
@@ -128,7 +128,7 @@ Namespaces
 ==========
 
 The migration library can automatically scan all namespaces you have defined within
-**application/Config/Autoload.php** and its ``$psr4`` property for matching directory
+**app/Config/Autoload.php** and its ``$psr4`` property for matching directory
 names. It will include all migrations it finds in Database/Migrations.
 
 Each namespace has it's own version sequence, this will help you upgrade and downgrade each module (namespace) without affecting other namespaces.
@@ -149,7 +149,7 @@ re-usable, modular code suites.
 Usage Example
 *************
 
-In this example some simple code is placed in **application/Controllers/Migrate.php**
+In this example some simple code is placed in **app/Controllers/Migrate.php**
 to update the schema::
 
 	<?php
@@ -265,7 +265,7 @@ You can use (refresh) with the following options:
 
 **create**
 
-Creates a skeleton migration file in **application/Database/Migrations**.
+Creates a skeleton migration file in **app/Database/Migrations**.
 
 - When migration type is timestamp, using the YYYYMMDDHHIISS format::
 
@@ -283,7 +283,7 @@ You can use (create) with the following options:
 Migration Preferences
 *********************
 
-The following is a table of all the config options for migrations, available in **application/Config/Migrations.php**.
+The following is a table of all the config options for migrations, available in **app/Config/Migrations.php**.
 
 ========================== ====================== ========================== =============================================================
 Preference                 Default                Options                    Description
@@ -308,7 +308,7 @@ Class Reference
 		:rtype:	mixed
 
 		Migrates up to the current version (whatever is set for
-		``$currentVersion`` in *application/Config/Migrations.php*).
+		``$currentVersion`` in *app/Config/Migrations.php*).
 
 	.. php:method:: findMigrations()
 
diff --git a/user_guide_src/source/dbmgmt/seeds.rst b/user_guide_src/source/dbmgmt/seeds.rst
index efdf999bdf..5f0cb0450d 100644
--- a/user_guide_src/source/dbmgmt/seeds.rst
+++ b/user_guide_src/source/dbmgmt/seeds.rst
@@ -10,10 +10,10 @@ event or setting information, and more.
 Database seeds are simple classes that must have a **run()** method, and extend **CodeIgniter\Database\Seeder**.
 Within the **run()** the class can create any form of data that it needs to. It has access to the database
 connection and the forge through ``$this->db`` and ``$this->forge``, respectively. Seed files must be
-stored within the **application/Database/Seeds** directory. The name of the file must match the name of the class.
+stored within the **app/Database/Seeds** directory. The name of the file must match the name of the class.
 ::
 
-	// application/Database/Seeds/SimpleSeeder.php
+	// app/Database/Seeds/SimpleSeeder.php
 	class SimpleSeeder extends \CodeIgniter\Database\Seeder
 	{
 		public function run()
diff --git a/user_guide_src/source/general/common_functions.rst b/user_guide_src/source/general/common_functions.rst
index 8a2d844f6e..7229668d38 100755
--- a/user_guide_src/source/general/common_functions.rst
+++ b/user_guide_src/source/general/common_functions.rst
@@ -322,7 +322,7 @@ Core Constants
 
 .. php:const:: APPPATH
 
-	The path to the **application** directory.
+	The path to the **app** directory.
 
 .. php:const:: ROOTPATH
 
diff --git a/user_guide_src/source/general/errors.rst b/user_guide_src/source/general/errors.rst
index 7d6f2ab641..11bb186167 100644
--- a/user_guide_src/source/general/errors.rst
+++ b/user_guide_src/source/general/errors.rst
@@ -93,7 +93,7 @@ PageNotFoundException
 ---------------------
 
 This is used to signal a 404, Page Not Found error. When thrown, the system will show the view found at
-``/application/views/errors/html/error_404.php``. You should customize all of the error views for your site.
+``/app/views/errors/html/error_404.php``. You should customize all of the error views for your site.
 If, in ``Config/Routes.php``, you have specified a 404 Override, that will be called instead of the standard
 404 page::
 
diff --git a/user_guide_src/source/installation/downloads.rst b/user_guide_src/source/installation/downloads.rst
index cce40bce34..956d4e0f4c 100644
--- a/user_guide_src/source/installation/downloads.rst
+++ b/user_guide_src/source/installation/downloads.rst
@@ -2,32 +2,32 @@
 Downloading CodeIgniter
 #######################
 
-The CodeIgniter 4 open source project has its own 
+The CodeIgniter 4 open source project has its own
 `Github organization <https://github.com/codeigniter4>`_.
 
 There are a number of repositories there of interest:
 
-- `CodeIgniter4 <https://github.com/codeigniter4/CodeIgniter4>`_ 
+- `CodeIgniter4 <https://github.com/codeigniter4/CodeIgniter4>`_
     holds the codebase for the project, including unit testing
     and the source from which the user guide is built.
     This would be used by contributors to the project.
-- `framework <https://github.com/codeigniter4/framework>`_ 
+- `framework <https://github.com/codeigniter4/framework>`_
     holds the released versions of the framework.
     This would be normally be used by developers.
-- `appstarter <https://github.com/codeigniter4/appstarter>`_ 
-    holds the released application starter, with application
+- `appstarter <https://github.com/codeigniter4/appstarter>`_
+    holds the released application starter, with app
     and public folders, but with only a composer
     dependency on the framework.
     This is meant as the easy way to start a CodeIgniter 4 project.
-- `userguide <https://github.com/codeigniter4/userguide>`_ 
+- `userguide <https://github.com/codeigniter4/userguide>`_
     holds the pre-built user guide. It can be downloaded
     on its own, or `viewed online <https://codeigniter4.github.io/userguide>`_.
-- `translations <https://github.com/codeigniter4/translations>`_ 
+- `translations <https://github.com/codeigniter4/translations>`_
     holds translations of the CodeIgniter 4 system messages.
     Developers can use this for :doc:`localization </outgoing/localization>`.
-- `coding-standard <https://github.com/codeigniter4/coding-standard>`_ 
+- `coding-standard <https://github.com/codeigniter4/coding-standard>`_
     holds the coding conventions we use for source code that is
-    part of the framework itself. 
+    part of the framework itself.
     It is a dependency of the codebase repository, for contributors.
 
 In all the above, the latest version of a repository can be downloaded
diff --git a/user_guide_src/source/outgoing/response.rst b/user_guide_src/source/outgoing/response.rst
index 9c33996d4c..93bb478986 100644
--- a/user_guide_src/source/outgoing/response.rst
+++ b/user_guide_src/source/outgoing/response.rst
@@ -155,12 +155,12 @@ Turning CSP On
 --------------
 
 By default, support for this is off. To enable support in your application, edit the ``CSPEnabled`` value in
-**application/Config/App.php**::
+**app/Config/App.php**::
 
 	public $CSPEnabled = true;
 
 When enabled, the response object will contain an instance of ``CodeIgniter\HTTP\ContentSecurityPolicy``. The
-values set in **application/Config/ContentSecurityPolicy.php** are applied to that instance and, if no changes are
+values set in **app/Config/ContentSecurityPolicy.php** are applied to that instance and, if no changes are
 needed during runtime, then the correctly formatted header is sent and you're all done.
 
 Runtime Configuration
@@ -440,7 +440,7 @@ The methods provided by the parent class that are available are:
 
 		The prefix is only needed if you need to avoid name collisions with
 		other identically named cookies for your server.
-                
+
 		Provide a prefix if cookies should only be deleted for that subset.
                 Provide a domain name if cookies should only be deleted for that domain.
                 Provide a path name if cookies should only be deleted for that path.
diff --git a/user_guide_src/source/outgoing/view_parser.rst b/user_guide_src/source/outgoing/view_parser.rst
index 805a4f0eb6..410d182b55 100644
--- a/user_guide_src/source/outgoing/view_parser.rst
+++ b/user_guide_src/source/outgoing/view_parser.rst
@@ -440,7 +440,7 @@ See `PHP's NumberFormatter <http://php.net/manual/en/numberformatter.create.php>
 Custom Filters
 --------------
 
-You can easily create your own filters by editing **application/Config/View.php** and adding new entries to the
+You can easily create your own filters by editing **app/Config/View.php** and adding new entries to the
 ``$filters`` array. Each key is the name of the filter is called by in the view, and its value is any valid PHP
 callable::
 
@@ -452,7 +452,7 @@ callable::
 PHP Native functions as Filters
 -------------------------------
 
-You can easily use native php function as filters by editing **application/Config/View.php** and adding new entries to the
+You can easily use native php function as filters by editing **app/Config/View.php** and adding new entries to the
 ``$filters`` array.Each key is the name of the native PHP function is called by in the view, and its value is any valid native PHP
 function prefixed with::
 
diff --git a/user_guide_src/source/testing/debugging.rst b/user_guide_src/source/testing/debugging.rst
index ab79a8d6fc..d35bd21b16 100644
--- a/user_guide_src/source/testing/debugging.rst
+++ b/user_guide_src/source/testing/debugging.rst
@@ -61,11 +61,11 @@ Enabling the Toolbar
 
 The toolbar is enabled by default in any environment *except* production. It will be shown whenever the
 constant CI_DEBUG is defined and it's value is positive. This is defined in the boot files (i.e.
-application/Config/Boot/development.php) and can be modified there to determine what environments it shows
+app/Config/Boot/development.php) and can be modified there to determine what environments it shows
 itself in.
 
 The toolbar itself is displayed as an :doc:`After Filter </incoming/filters>`. You can stop it from ever
-running by removing it from the ``$globals`` property of **application/Config/Filters.php**.
+running by removing it from the ``$globals`` property of **app/Config/Filters.php**.
 
 Choosing What to Show
 ---------------------
diff --git a/user_guide_src/source/testing/overview.rst b/user_guide_src/source/testing/overview.rst
index 4e006a4128..0f11a0b729 100644
--- a/user_guide_src/source/testing/overview.rst
+++ b/user_guide_src/source/testing/overview.rst
@@ -216,7 +216,7 @@ parameter is the name of the property to set the value of. The third parameter i
 Mocking Services
 ================
 
-You will often find that you need to mock one of the services defined in **application/Config/Services.php** to limit
+You will often find that you need to mock one of the services defined in **app/Config/Services.php** to limit
 your tests to only the code in question, while simulating various responses from the services. This is especially
 true when testing controllers and other integration testing. The **Services** class provides two methods to make this
 simple: ``injectMock()``, and ``reset()``.
diff --git a/user_guide_src/source/tutorial/static_pages.rst b/user_guide_src/source/tutorial/static_pages.rst
index c8a408eaea..52c2d0f061 100644
--- a/user_guide_src/source/tutorial/static_pages.rst
+++ b/user_guide_src/source/tutorial/static_pages.rst
@@ -24,7 +24,7 @@ you'll see URL patterns that match:
 As URL schemes become more complex, this may change. But for now, this
 is all we will need to know.
 
-Create a file at *application/Controllers/Pages.php* with the following
+Create a file at *app/Controllers/Pages.php* with the following
 code.
 
 ::
@@ -53,7 +53,7 @@ Now that you've created your first method, it's time to make some basic page
 templates. We will be creating two "views" (page templates) that act as
 our page footer and header.
 
-Create the header at *application/Views/templates/header.php* and add
+Create the header at *app/Views/templates/header.php* and add
 the following code:
 
 ::
@@ -70,7 +70,7 @@ the following code:
 The header contains the basic HTML code that you'll want to display
 before loading the main view, together with a heading. It will also
 output the ``$title`` variable, which we'll define later in the controller.
-Now, create a footer at *application/Views/templates/footer.php* that
+Now, create a footer at *app/Views/templates/footer.php* that
 includes the following code:
 
 ::
@@ -84,7 +84,7 @@ Adding logic to the controller
 
 Earlier you set up a controller with a ``view()`` method. The method
 accepts one parameter, which is the name of the page to be loaded. The
-static page templates will be located in the *application/Views/pages/*
+static page templates will be located in the *app/Views/pages/*
 directory.
 
 In that directory, create two files named *home.php* and *about.php*.
@@ -166,7 +166,7 @@ controller you made above produces...
 - ``localhost:8080/pages/view/about`` will show the "about" page that you made above,
   because we explicitly asked for it
 - ``localhost:8080/pages/view/shop`` will show a "404 - File Not Found" error page,
-  because there is no `application/Views/pages/shop.php`
+  because there is no `app/Views/pages/shop.php`
 
 
 Routing
@@ -179,7 +179,7 @@ controller and method, and break free from the normal convention:
 ``http://example.com/[controller-class]/[controller-method]/[arguments]``
 
 Let's do that. Open the routing file located at
-*application/Config/Routes.php* and look for the "Route Definitions"
+*app/Config/Routes.php* and look for the "Route Definitions"
 section of the configuration file.
 
 The only uncommented line there to start with should be:::